<template>
  <div>
    <router-link v-show="showTop" tag="div" to="/" class="header-abs">
      <div class="iconfont header-abs-icon">&#xe624;</div>
    </router-link>
    <div class="header-fixed" v-show="!showTop" :style="opacityStyle">
        景点详情
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  props: {

  },
  data () {
    return {
      showTop: true,
      opacityStyle: {
        opacity: 0
      },
      timer: null
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop || document.body.scrollTop
      if (this.timer) {
        clearTimeout(this.timer)
      }
      this.timer = setTimeout(() => {
        if (top > 60) {
          let opacity = top / 140
          opacity = opacity > 1 ? 1 : opacity
          this.opacityStyle = { opacity }
          this.showTop = false
        } else {
          this.showTop = true
        }
      }, 16)
    }
  },
  mounted () {
    window.addEventListener('scroll', this.handleScroll)
  },
  beforeDestroy () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
// beforeDestroy队全局事件解绑
</script>

<style lang="stylus" scoped>
 @import '~styles/varibles.styl'
  .header-abs
    position: absolute
    left: .2rem
    top: .2rem
    width: .8rem
    height: .8rem
    line-height: .8rem
    text-align: center
    border-radius: .4rem
    background: rgba(0, 0, 0, .8)
    .header-abs-icon
      font-size: .4rem
      color: #fff
  .header-fixed
    z-index: 2
    position: fixed
    top: 0
    left: 0
    right: 0
    overflow: hidden
    height: $headerHeight
    line-height: $headerHeight
    text-align: center
    color: #fff
    background: $bgColor
    font-size: .32rem
    .header-fixed-back
      position: absolute
      top: 0
      left: 0
      width: .64rem
      text-align: center
      font-size: .4rem
      color: #fff
</style>
